High voltage switch technology is used in many areas such as laser technology, lightening protection devices and other areas requiring the switching of high voltage. Spark gaps are often used as effective high voltage switches, the technology of which is summarized in a paper by Tommy R. Burkes et al, A Review of High Power Switching Technology, IEEE Transactions on Electron Devices, Volume ED-26, No. 10, October 1979, 1405. Spark gaps commonly employ the use of a trigger arrangement to ionize the gap between the electrodes to cause a breakdown of the gap with a consequent discharge arc between the electrodes. In using a trigger arrangement, if the potential between the spark gap electrodes is at a sufficiently high potential for the spacing, the ionizing of the gas in the gap by triggering the arrangement with a trigger signal provides a selectively operable high voltage switch.
To improve the firing of the trigger arrangement, a dielectric material may be used as spaced between the trigger electrodes. According to Lavoie et al in their paper "Spark Chamber Pulsing System", The Review of Scientific Instruments, Volume 34, No. 41, November 1964, 1567, such use of a dielectric material reduces the voltage requirements in the signal to trigger a main discharge in the spark gap. According to this paper, barium titanate having a high dielectric constant is useful.
It is common to use a spark gap in laser circuitry to reduce almost instantaneously the potential of one of the electrodes of a laser cavity to excite the cavity region and roduce lasing action. Hasson, U.S. Pat. No. 4,035,683 discloses the use of a spark gap with a laser cavity to control the timing in initiating or commencing the lasing action of a laser. The important aspects in using a spark gap for a laser is that the jitter time, that is the period from when the trigger signal is applied to the trigger arrangement and the discharge arc occurs in the spark gap, is reasonably constant. In some laser applications, a jitter of only three to five nanoseconds is desirable.
A spark gap using a high dielectric constant material between the trigger pin and the trigger electrode, such as the arrangement of Lavoie et al where the main discharge is between the high voltage electrode and the trigger electrode configuration, is particularly advantageous for use with lasers. Only a comparatively low voltage is necessary to pulse the trigger pin to cause a sufficient electron and ion density in the spark gap to provide breakdown and consequent arcing in the spark gap. However, it has been found that the solid high dielectric constant material is chipped away or fractured by the intensity of the discharge arc as it travels to the adjacent trigger electrode. As the barium titanate is worn away by the discharge arc, jitter of the spark gap is increased and the arrangement becomes impractical from a precise switching standpoint and may become inoperable.
The spark gap, according to this invention, overcomes the above problem, has extended life and the capability of producing relatively low jitter so that the spark gap is particularly useful with lasers.